What model of camcorder is your original video coming from and what format and resolution is it?
Which version of the program are you using and on what operating system? Is it the same operating system that you were using when the program used to work?
Which Publish & Share template are you using to output your video?
Have you checked your output video on more than one player? Windows Media Player, for instance, can have trouble playing some files. A player like the excellent free VLC Media Player can play almost any format and is a much better tool to test drive your finished videos on.